Hydraulic reversing system for a reciprocating working member

ABSTRACT

A HYDRAULIC REVERSING SYSTEM FOR A RECIPROCATING WORKING MEMBER WHICH IS CONNECTED WITH A POWER CYLINDER RECEIVING A MAIN PISTON WHICH SUBDIVIDES THE CYLINDER INTO DISPACEMENT CHAMBERS. THE MAIN CONTROL VALVE COMPRISES A PISTON WITH A CENTRAL SPOOL SEPARATING TWO WORKING CHAMBERS FROM ONE ANOTHER THE WORKING CHAMBERS BEING CONNECTED TO THE DISPLACEMENT CHAMBERS OF THE MAIN CYLINDER. IN ADDITION, A PAIR OF CONTROL SPOOLS SEPARATE THE MAIN CHAMBERS OF THE VALVE FROM CONTROL CHAMBERS WHICH ARE RESPECTIVELY CONNECTED BY HYDRAULIC IMPULSE TRANSMITTERS COOPERATING WITH THE MOVABLE MEMBER FOR ALTERNATE OPERATION ON RECIPROCATION THEREOF. IMMEDIATELY UPON TRIPPING OF ONE OF THE IMPULSE GENERATORS, AND OIL FLOW FROM THE MAIN VALVE INLET TO THE CORRESPONDING CONTROL COMPARTMENT IS TERMINATED AND THE SPOON VALVE SHIFTED IN THE OPPOSITE DIRECTION TO REVERSE THE FLOW OF FLUID TO THE DISPLACEMENT COMPARTMENTS OF THE MAIN CYLINDER. AFTER AN INITIAL CLEARANCE IS FORMED IN COMMINICATION WITH THE CONTROL CHAMBER, THE MAIN HYDRAULIC PRESSURE SERVES TO BIAS THE CONTROL VALVE.

Nov. 16, 1971 P. FUHRIMANN 3,620,125

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United States Patent O land Filed June 4, 1969, Ser. No. 830,261 Claims priority, application Switzerland, June 19, 1968, 9,462/68 Int. Cl. F011 25/02 U.S. Cl. 91-280 6 Claims ABSTRACT OF THE DISCLOSURE A hydraulic reversing system for a reciprocating working member which is connected with a power cylinder receiving a main piston which subdivides the cylinder into displacement chambers. The main control valve comprises a piston with a central spool separating two working chambers from one another the Working chambers being connected to the displacement chambers of the main cylinder. In addition, a pair of control spools separate the main chambers of the valve from control chambers which are respectively connected to hydraulic impulse transmitters cooperating with the movable member for alternate operation on reciprocation thereof. Immediately upon tripping of one of the impulse generators, an oil flow from the main valve inlet to the corresponding control compartment is terminated and the spool valve shifted in the opposite direction to reverse the ow of Huid to the displacement compartments of the main cylinder. After an initial clearance is formed in communication with the control chamber, the main hydraulic pressure serves to bias the control valve.

This invention relates to a fully hydraulic device on a machine or apparatus having a part reciprocating in a straight line, for precision reversing of the movement of the part between two adjustable turnround (reversal) points in a manner substantially independent of load and velocity, the device including a pressurized-oil pump, land one or more impulse transmitter plungers actuated by the moving part.

Where it is required, in a known system, to keep parts of machines or apparatus in reciprocating movement with the aid of simple oil-operated drives, electromagnetically actuated hydraulic multi-way valves are used and are excited by electric impulse switches allocated to stops on the reciprocating part of the machine or apparatus. The contacts given in this way, however, only trip the electric impulse and thus the braking phase, so that the effective braking paths after the reversing impulse are of varying length, according to the set velocity and the masses in motion. This known system consequently has a pronounced defect, inasmuch as the effective strokes cannot be speedily determined, according to the required operating characteristics, which is disadvantageous, particularly with rapid reciprocating movements and short strokes, as in the winding of yarns, or when the machine moves against an obstruction, as in metal-cutting operations such as planing.

Methods of remedying these defects have already been proposed, as for instance systems with electric and electronic time relays or the much more complex systems with hydraulically timed time movements. All these defects can now be obviated through the present invention. To make this possible, the device according to the invention is so designed that as soon as the impulse movement has been tripped the impulse transmitter plunger in question closes an overow pipe leading to the oil tanks (reservoir), whereupon the oil displaced Patented Nov. 16, 1971 by the plunger flows through an oil pipe and moves the piston of the control valve into its middle blocking position, thereby freeing an annular clearance for the entry of control oil coming either through a throttle from the main pressurized-oil pipe or directly from an auxiliary pump, so that the piston of the main control valve is displaced into its opposite end position and the valve initiates the re-acceleration of the working piston, while the same control oil returns the impulse transmitter into its initial position and the plunger thereby re-opens the overflow connection to the oil tank for an intermediate rinsing with control oil and an effective venting of the impulse control-oil pipe.

The accompanying drawing shows by way of example some embodiments of the fully hydraulic device according to the invention.

FIG. 1 shows a diagrammatic representation of a first fully hydraulic device such as can be used to advantage where small or insignificant load changes are to be expected, as for instance in the thread guides of winding mechanisms;

FIG. 2 shows the device represented in FIG. l with individual parts in other positions;

FIG. 3 shows diagrammatically a second device which can be used to advantage where large load changes are to be expected, as for instance in a simple shaping machine with various cutting adjustments;

FIG. 4 is a diagrammatic view of a third device for use in large metal-cutting machines, for instance parallel planing machines;

FIG. 5 is an axial section through the main control valve, and

FIG. 6 shows an impulse transmitter, also in axial section.

Referring to FIG. 1, numeral 1 denotes an oil tank from which a suction pipe 2 leads to a pressure pump 3. From this a pressurized-oil pipe 4, having a volumetric flow regulator S fitted therein, leads to the hydraulic control valve 6. This consists essentially of the body or housing 6a (FIGS. 1 and 5) and the piston (6k, 6I, 6m) which is axially movable therein. Numerals 6b to 6i designate various oil chambers of the valve body 6a. Two pipes 9a and 9b lead from chambers 6b and 6c to the displacement spaces 10a and 10b of the working cylinder 10 having therein an axially movable piston 10d mounted on a piston rod 10c. This piston road 10c is connected (in a way not shown) with the part of the machine or apparatus which performs a reciprocating movement. At its two ends piston rod 10c` carries two reversing elements 11 and 12, each of which is provided with a slanting contact surface 11a and 12a respectively.

Two hydraulic impulse transmitters 13 and 14 are located at any desired position on the frame of the machine or apparatus. They each consist of a cylinder 13a or 14a and a plunger that can move inside it. The plungers are fitted with rods projecting from cylinders 13a or 14a, the ends 13e and 14C of which rods project into the path of the reversing elements 11 and 12 or more exactly of their contact surfaces 11a and 12a respectively. Overilows 13d and 14d are arranged in cylinders 13 and 14 and are open when plungers 13b and 14b are in the upper limiting position shown in FIG. 1, but are covered as the plungers move downwards. Pipes 15 and 16 lead from said overflows 13d and 14d back into the oil tank. Displacement spaces 13a and 14a of the impulse transmitters 13 and 14 are each connected through a pipe 17 or 18 to the oil chambers 6h and 6i respectively of the control valve. Said pipes have fitted therein a nonreturn valve 19 or 20 which can be bypassed by an adjustable throttle valve 21 or 22 respectively.

In the following description of the operations of the device let it be assumed that the various parts are in the position shown in FIG. 1. Oil supplied by pump 3 flows through delivery pipe 4 and flow regulator 5 into chamber 6c of the control valve, whence through pipe 9b into space b of working cylinder 10, so that piston 10d, piston rod 10c and the part of the machine or apparatus connected to the latter are moved to the left in the direction of the arrow A in FIG. 1. The oil present in space 10a is thereby forced out and ows back through pipe 9a, the communicating chambers 6b and 6d of the control valve and pipe 7a and 7d into the oil tank 1.

In the further course of the movement of working piston 10d in the direction of arrow A, the contact surface 11a of the reversing element 11 comes up against the end 13C of the plunger rod, plunger 13b of the impulse transmitter being pushed downwards and the overflow 13d will be closed at the very outset of this movement. The oil displaced from space 13a of the impulse transmitter now flows through the comparatively narrow pipe 17 and via throttle valve 21 into oil chamber 6h of the control valve, so that the piston moves to the right in body 6a. In the process the opening between chambers 6d and 6b is narrowed more and more by the piston section 61 so that the resistance to the oil escaping from space 10a of working cylinder 10 becomes greater and greater and the movement of piston 10d, piston rod 10c and the part of the machine or apparatus connected thereto is thereby increasingly braked.

The diameter and stroke of the plunger 13b and the swept volume of the control valve are so attuned to each other that at the end of the movement of piston rod 10c and plunger 13b the control valve 6 comes into the middle position shown in FIG. 2, in which the piston section 6k shuts off the pressurized-oil pipe 4. In the course of the movement of the piston of control valve 6 to the right, as described above, the oil present in chamber 6i is displaced and liows through throttle valve 22, pipe 18, space 14a of impulse transmitter 14 and overflow 14d, thereby raising plunger 14b into its upper end position, then through pipe 16 back into the oil tank.

In the middle position of the piston of control valve 6 shown in FIG. 2 the piston section 6l leaves a narrow annular clearance between chambers 6i and 6h. As a result pressurized oil Hows from delivery pipe 4 through pipe 23 with a permanently adjusted throttle 22' into chamber 6h so as to cause piston of the control valve to move still further to the right. In the middle position of the servo-piston valve as in FIG. 2, piston section 6m leaves a narrow annular clearance c free between chambers 6g and 61', so that oil from delivery pipe 4 also ows through pipe 24 with its built-in throttle 25 into chamber 6i. This oil does not have any effect on the piston, however, as it can escape through throttle valve 22, pipe 18, overow 14d and pipe 16 into the oil tank. This arrangement ensures constant venting and the supply of the necessary amount of oil to the impulse transmitter.

As the piston of control valve 6 reaches its right-hand end position, piston section 6k frees the entry of delivery pipe 4 to chamber 6b so that pressurized oil flows through pipe 9a into space 10a of the working cylinder. Piston 10d, piston rod 10c and the part of the machine or apparatus connected thereto are thus moved to the right in the direction of the arrow B in FIG. 2, and the oil forced out of space 10b can flow back into oil tank 1 through pipe 9b, chambers 6c and 6e, pipes 7b and 7d and the nonreturn valve 8.

As visible from FIG. 6, the small plungers of the impulse transmitters are loaded by springs 13e and 14e, which tend to keep plungers 13b and 14b in their upper end position.

In the embodiment shown in FIG. 3, numeral 1 again designates the oil tank, 2 the suction pipe, 3 the oil pump, 4 at the delivery pipe, 6 the control valve, 9a and 9b the pipes leading from the latter to the displacement spaces 10a and 10b of the working cylinder, 11 and 12 the reversing elements mounted on piston rod 10c with its piston 4 10d, 13 and 14 the impulse transmitters, l5 and 16 the overflow pipes, 17 and 18 the pipes connecting the impulse transmitters to the control valve with their non-return valves 19 and 20 and the throttle valves 21 and 22 respectively fitted in parallel therewith.

As a contrast to the embodiment shown in FIGS. 1 and 2, pipes 23 and 24 leading to chambers 6j and 6g of the control valve are in this case connected to delivery pipe 4 not beyond the ow regulator 5 but at point 26 in advance thereof. Furthermore, two flow regulators 27 and 28 are tted in the two control-oil supply pipes 23 and 24 instead of the fixed throttles 22 and 25 respectively. These make it possible to adjust the acceleration phase even better. This is of some importance particularly in view of the large and possible changing loads which may have to be accelerated and slowed down. Otherwise the modus operandi of the device shown in FIG. 3 corresponds to that of the device shown in FIGS. 1 and 2.

In the form of embodiment shown in FIG. 4, numeral 1 again designates the oil tank, 2 the suction pipe, 3 the pressure pump, 4 the delivery pipe leading to the control valve 6; 9a and 9b the pipes leading from the latter to the working cylinder 10; 10d the working piston with piston road 10c and reversing elements 11 and l2 attached thereto, 13 and 14 the impulse transmitters with overow pipes 1S and 16; 17 and 18 the pipes leading from the impulse transmitters to the control valve 6 with their non-return valves 19 and 20 and the throttle valves 21 and 22 respectively fitted in parallel therewith.

The embodiment shown in FIG. 4 differs from the two forms described hereinbefore in that pump 3 is arranged for electric adjustment of delivery, being in addition equipped with slip compensation to counterbalance its internal leakage losses, according to load and pressure. In this embodiment the device is also provided with an auxiliary pump 29 for constant delivery. A pipe 30 leads from this auxiliary pump 29 to an auxiliary control valve 31 fitted in advance of the working cylinder 10 and designed as a four-way slide valve. From this four-way valve two pipes 32 and 33 branch off to pipes 9a and 9b respectively, while a further pipe 34 leads to the oil tank. 'Iiwo further pipes 37 and 38 lead from auxiliary pump 29 by way of ow regulators 3S and 36 to chambers 6f and 6g of the main control valve 6 respectively. It will be apparent that the pump 29 serves also to determine the displacement rate of the control piston since this pump alone constitutes its source of control uid. Auxiliary pump 29, in conjunction with the four-way valve 31, permits working cylinder 1I] to be operated at low speed without the main operating pump 3, which is adjusted to the working speed.

The embodiment of FIG. 4 represents a system in which the auxiliary pump 29 is connected via the line 30 and a further control valve 31 to the lines 32, 33 supplying the main working chambers of the power cylinder means 10. When the valve 31 is switched into its craw position in either direction, the tluid from the auxiliary pump is delivered to one of the chambers of the power cylinder and returned to the reservoir from the other chamber. The valve 31 thus allows the power cylinder to be controlled solely by the supply rate of the auxiliary pump 29 when slow displacement of the hydraulic member is desired.

In cases in which small loads only have to be moved backwards and forwards, as for instance thread guides, which have a short braking path, the impulse transmitter plungers can be actuated directly by piston rod 10c or the part of the machine or apparatus connected thereto, i.e. without the use of the slanting contact surfaces 11a and 12a., in which case the impulse transmitter plunger rods face each other in the direction of motion.

tlf on the other hand machine tables have to be reversed, as for instance in small or heavy machine-tools, such as parallel planing machines, reversing cams or contact surfaces are to be recommended adapted to translate the stroke of the impulse transmitter plungers arranged at right angles to the stroke of the working piston in accordance with the braking distance and which can also run over at crawling speed with the oil from auxiliary pump 29 when the main pump is switched olf.

It is preferable for control valve 6 to be so designed that in the middle position of the piston (FIG. the two sealing edges 6k' and 6k", as well as the inner sealing edges 6l" and 6m" of the two outer piston collars 6l and 6m, are ilush with or lie in the same plane as the sealing edges 4', 4", 6d and 6e' of the outlet of delivery pipe 4 and oil chambers 6d and 6e, so that they result in linear sealing as opposed to surface sealing, while the outer edges 6l and 6m of piston collars 6l and 6m are set back in relation to the edges 6;" and 6g of the ol chambers f and 6g respectively and thus form an annular clearance C'.

`It is also possible to have the adjustable throttling and nonreturn valves 19, 21 and 20, 22 incorporated in the body 6a of control valve, as diagrammatically shown in FIG. 5.

What I claim is:

1. A hydraulic reversing system for a reciprocating working member comprising:

power-cylinder means including at least one power piston connected with said member for displacing same and a pair of main chambers for pressurization of the piston to urge said member in opposite direction;

a source of fluid under pressure and including at least one pump;

a control valve including a housing and a valve piston shiftable in said housing and subdividing same into a pair of main compartments respectively connected with said chambers and alternately connectable with said pump upon reciprocation of said valve piston in opposite directions, said valve piston further defining in said housing a pair of oppositely elfective control compartments respectively connected with said source; and

a pair of hydraulic impulse transmitters each connected with a respective one of said control chambers and provided with an overow permitting the outliow of iluid from the respective control chamber, and with a plunger actuatable by said member upon movement thereof in a respective direction to block said overl tliow and thereby pressurize the respective control chamber to bias said valve piston in an opposite direction and consequent pressurization of said power-cylinder means to displace said member in the opposite direction, said valve being so constructed and arranged that the uid in said control compartments biases a displaced one of said plungers into an initial position to reopen the respective overflow.

2. The system defined in claim 1, further comprising an adjustable throttle and a one-way valve in parallel therewith between each of said control compartments and the respective impulse transmitter.

3. The system defined in claim 1 wherein said source includes respective ducts connecting the discharge side of said pump with the respective control compartment upon displacement of said valve system to define an annular clearance in said housing communicating with the latter, said ducts each being formed with a respective pressure independent ow regulator.

4. The system dened in claim 1 wherein said source includes an auxiliary pump operating independently of the first-mentioned pump and a further valve connecting said auxiliary pump with said power cylinder means for crawling-speed operation thereof.

5. The system defined in claim 2 wherein said throttle and one-way valves are built into said housing.

6. The system detined in clairn 1 wherein said piston has a central spool having a pair of sealing edges and a pair of outer spools each defining an annular clearance with said housing communicating with a respective one of said control compartments upon movement of said valve piston in the direction of the other control compartments, said housing being provided with an inlet connected with said source and normally blocked by said central spool in an intermediate position of said valve piston, a pair of outlets anking said central spool in said intermediate position and communicating with the respective chambers of said power-cylinder means, and further inlets communicating with said clearances and controlled by said outer spools while being connected to said source.

References Cited UNITED STATES PATENTS 2,615,433 10/1952 Deardorl et al 91-426 3,130,528 4/1964 Andersen 91-306 X 3,162,093 12/1964 Zoller 91-306 3,174,409 3/1965 Hill 91-306 ALLAN D. HERRMANN, Primary Examiner U.S. Cl. XfR. 

